This invention relates, in general, to fluid heater apparatus and, more particularly, to fluid heater apparatus which provide a heated wash fluid to a cleanable surface, and, still more specifically, to a heated wash fluid apparatus for a vehicle windshield wash system.
It is necessary in many diverse applications to quickly elevate the temperature of a fluid to a higher use temperature. For example, it is desirable to be able to provide instant hot water, for use in homes, offices and campers, as well as for industrial processes.
In cleaning applications, it is known that hot fluid removes dirt and other debris from a surface much better and much faster than colder fluids. One heated fluid application is a vehicle wash fluid system, such as a windshield wash system as well as vehicle wash systems applied to camera lenses, exterior lamps and lamp lenses, mirrors, etc. Vehicles are typically provided with at least one and usually multiple windshield washers which are used to clear the field of vision in a windshield or rear backlight.
Typically, a nozzle or spray device is provided adjacent to or as part of the windshield wiper to disperse a pattern of wash fluid onto the windshield prior to and during the wiping operation to improve the efficiency of the wiping operation so as to provide a clear field of vision for the driver or vehicle passengers. The wash fluid is typically stored in a reservoir in the engine compartment and is pumped through the spray device upon manual activation of a control actuator by the vehicle driver.
Since it is known that warm or heated fluid provides better cleaning efficiency than cold fluid, it is known to provide a heated wash fluid to a vehicle window spray device. Various wash fluid heating devices have been developed, but all typically utilize a heat exchanger design wherein a heat source is disposed in a body through which the wash fluid flows. The wash fluid picks up heat in the heat exchange body which elevates its temperature prior to dispersion through the spray nozzle onto a vehicle window.
However, such prior wash fluid heating devices are inefficient in terms of heat transfer capability as well as being able to only provide a small quantity or a short duration of heated wash fluid onto a vehicle window. Further, direct contact of the fluid with the heat source causes higher temperature hot spots in the fluid and lower temperature fluid portions which do not contact the heat source.
The control circuit used to operate such windshield wash fluid heating devices must provide high amperage such as 50 amps at 12 volts. The switching devices in the control circuit, which typically utilize MOSFETs, generate considerable heat themselves, but still must be thermally insulated from the heated fluid.
However, the temperature of the primary heating source and the heated fluid is much greater than the heat generated by the MOSFETs so that heat escaping from the thermal mass of the body of the heating device heats the upper portion of the heating device if the temperature gradient between the heating device and the surrounding ambient temperature across the upper plate or surface of the heating device is too high.
Thus, it would be desirable to provide a fluid heater apparatus which provides a heated fluid in an efficient manner, which has improved operating efficiency, which provides heat balancing for the thermal mass, which balances the heating device temperature, and which reduces power consumption.